Achyuthan K E, Greenberg C S
J Biol Chem. 1987 Feb 5;262(4):1901-6.
Guanosine 5'-triphosphate (GTP) was found to inhibit guinea pig liver transglutaminase activity as measured by [3H]putrescine incorporation into casein. GDP and GTP-gamma-S also inhibited enzyme activity (GTP-gamma-S greater than GTP greater than GDP). Kinetic studies showed that GTP acted as a reversible, noncompetitive inhibitor and that CaCl2 partially reversed GTP inhibition. GTP also inhibited rat liver and adult bovine aortic endothelial cell transglutaminase, but did not inhibit Factor XIIIa activity. Guanosine monophosphate (GMP), cyclic GMP, and polyguanylic acid did not inhibit enzyme activity. Guinea pig liver transglutaminase adsorbed well to GTP-agarose affinity columns, but not to CTP-agarose columns, and the binding was inhibited by the presence of calcium ions. Specific binding of GTP to transglutaminase was demonstrated by photoaffinity labeling with 8-azidoguanosine 5'-[gamma-32P] triphosphate, which was inhibited by the presence of GTP or CaCl2. GTP inhibited trypsin proteolysis of guinea pig liver transglutaminase without affecting the trypsin proteolysis of chromogenic substrates. Proteolytic protection was reversed by the addition of calcium. This study demonstrates that GTP binds to transglutaminase and that both GTP and calcium ions function in concert to regulate transglutaminase structure and function.
通过测量[3H]腐胺掺入酪蛋白的量发现，鸟苷5'-三磷酸（GTP）可抑制豚鼠肝脏转谷氨酰胺酶的活性。GDP和GTP-γ-S也抑制该酶活性（GTP-γ-S＞GTP＞GDP）。动力学研究表明，GTP作为一种可逆的非竞争性抑制剂起作用，并且CaCl2可部分逆转GTP的抑制作用。GTP还抑制大鼠肝脏和成年牛主动脉内皮细胞的转谷氨酰胺酶，但不抑制因子XIIIa的活性。鸟苷一磷酸（GMP）、环鸟苷酸和聚鸟苷酸不抑制该酶活性。豚鼠肝脏转谷氨酰胺酶能很好地吸附到GTP-琼脂糖亲和柱上，但不能吸附到CTP-琼脂糖柱上，并且这种结合受到钙离子的抑制。通过用8-叠氮鸟苷5'-[γ-32P]三磷酸进行光亲和标记证明了GTP与转谷氨酰胺酶的特异性结合，GTP或CaCl2的存在可抑制这种结合。GTP抑制豚鼠肝脏转谷氨酰胺酶的胰蛋白酶水解，但不影响发色底物的胰蛋白酶水解。添加钙离子可逆转蛋白水解保护作用。本研究表明GTP与转谷氨酰胺酶结合，并且GTP和钙离子共同作用来调节转谷氨酰胺酶的结构和功能。
